New middle Miocene (Langhian - Serravallian) vertebrate localities in northwestern Patagonia, Argentina: A contribution to high latitude south american land mammal ages sequence

Abstract

The Miocene represents a key moment in the South American evolution, since meaningful geographic and climatic processes occurred, promoting the development of several biologic changes. The isolation of South America together with major global and regional climatic changes resulted in an enormous variety of biomes and endemic diversity of flora and fauna, especially of mammals diversity. Most of the best-known continental vertebrate fossil-bearing deposits correspond to the early and late Miocene, existing a deficient knowledge for the middle Miocene, which is poorly understood at high latitudes. This work examines four new middle Miocene fossiliferous localities from a North Patagonian foreland succession, through a multidisciplinary approach that combines stratigraphic and preliminary paleontological analyses within a previously defined high-resolution temporal scheme. Two localities are referred to the lower section of Collón Cura Formation, and were constrained to a range of 14.6–12.75 Ma, whereas the other two localities correspond to the upper section of Collón Cura Formation and were constrained to 12.75–12.05 Ma. A large variety of fossil vertebrates were recognized in the lower section, belonging to Teleostei, Testudinidae, Teiidae, Anura and Mammalia; whereas Teleostei, Testudinidae and Mammalia vertebrates were documented in the upper section. Our results indicate a Colloncuran and younger (e.g., Mayoan) South American Mammals Ages (SALMAs) for the lower and upper sections of Collón Cura Formation, respectively. However, data from this work support the idea of a continuum on the SALMAs sequence for the middle Miocene where overlap, at least partially, both in absolute dates and in the faunal assemblages.